Insulated electric connector



ct. 6, 1953 R. c. swENGEL INSULATED ELECTRIC CONNECTOR Original Filed Feb. 19, 1944 Tlclii l l I l l Il 'Ilm n INVENTOR: /Poaexr enfin/54 ATTORN s:

Patented Oct. 6, 1953 IN SULATED ELECTRIC CONNECTOR Robert C. Swcngel, York, Pa., assigner to Aircraft-Marine Products Inc., Harrisburg, Pa., a corporation of New Jersey Continuation of application Serial No. 523,004, February 19, 1944. This application October 16, 1951, Serial N o. 251,466

4 claims. (ol. 339-213) This invention relates to an insulated electric connector and the -method of attaching the same to a conductor end.

In the manufacture of electric connectors of the type adapted to be connected to the end of a conductor, it is often advantageous or desirable to insulate a portion of the connector, e. g. the ferrule of the connector which is attached to the conductor end. The connector is often attached to the conductor end by a crimping operation which not only assures a tight connection, but also one characterized by low resistance of er;- cellent stability by reason of intimate pressure contact between the metal of the connector and that of the conductor. As it is desirable to insulate the portion of the connector which is crimped onto the conductor ends, problems arise in elTecting a satisfactory and eicient insulation, it being expensive to insulate the connector after its attachment to the conductor. It had been suggested before my invention to cover the ferrule of such a connector with a sleeve of insulating plastic prior to the crimping operation by which the connector and conductor are compressed together as disclosed in Patent No.

2,410,321 of W. S. Watts; but because Iof the extremely high and localized pressures under the crimping dies, it may happen that portions of the insulating material are pierced or objectionably reduced in thickness by the jaws of the crimping tool when the crimps are made.

It is accordingly among the objects of my invention to provide a laminated electrical connection which is sturdy, durable and capable of application to a Wire or other electrical conductor by compressive Iforging therewith and of safe and emcient use after such application. Another object is to provide a connector of the crimped ferrule type wherein a portion which would be exposed to possible short circuits is protected therefrom by ample insulation. Another object is to provide a simple, practical and eilicient method of attaching an insulated connector to a conductor end in a manner which assures a tight connection of low stable resistance without damage to the unstripped insulation on the connector. Other objects will be in part apparent and in part pointed out hereinafter.

According to my present invention, a tubular piece of the insulation is adhesively secured to the base of the laminated connector, e. g. a metal ferrule of an electric connector is coated with a cement having such properties as enable it to adhere strongly both to the metal of the ferrule and to the insulating material which is to be applied on the ferrule. I have found that by coating the metal ferrule With a suitable cement, and then slipping over and shrinking onto the cement coating a tube formed of a suitable plastic having insualting properties, the tube is so firmly cemented to the ferrule that when the connector is crimped onto the end of a conductor the resistance of the material of the tube to puncture or near puncture at the crimped areas is greatly enhanced. f

The present application is an improvement on that of W. S. Watts described and `claimed in his Patent No. 2,410,321.

Although in the accompanying drawings I have shown a preferred embodiment of my invention and having described the same and various modications thereof in this specification, it is to be understood that these are not intended to be either exhaustive or at the ultimate limits of the invention, but, on the contrary, are chosen for the purposes of illustrating the invention in order that others skilled in the art may so fully understand the invention, its principles and the application thereof, that they may embody it and adapt itin numerous forms, each as may be best suited to the requirements of a particular use.

In the drawing, wherein there is shown one form of an insulated electric connector attached to a conductor in accordance with the method g `of my invention,

Figure 1 is a perspective view of the several elements of the connector, together with the conductor end to which the connector is to be attached;

Figure 2 is a perspective view of the connector attached to the conductor end; and

Figure 3 is an enlarged section taken along the line 3-3 of Figure 2.

Similar reference characters refer to similar parts throughout the views of the drawing.

In general, and with reference to Figure l, there is shown a connector generally indicated at I0 which comprises a ferrule or base I I from which extends an integral tongue I2. The outer end of tongue I2 carries a ring I3 which is adapted to be secured to a conventional binding post. As better shown in Figure 2, the stripped end Illa of a conductor I4 is disposed within ferrule II wherein it is securely held by a crimping operation which forges the ferrule tightly onto the conductor end. The outer surface of the ferrule is covered with an insulating sleeve, generally indicated at I5, this sleeve also being subjected to the crimping operation so that it tightly grips the ferrule.

I5, a metal tube I6 which may be formed of any malleable metal and which acts in a reinforcing capacity with respect to both theferrule LII and the insulating sleeve I8. Thus when the crimping operation takes place, tube I5 'prevents undue parting lof the ferrule sides at seam IIa and at the same time supports the sleeve I8 against transverse stretching forces.

rectly to the ferrule, as will be described.

The metal to which the insulating plastic is to be applied, in this case the tube IS, is according to this invention adhesively secured to the insulating sleeve. As illustrated, this is done by first .giving tube IS ya coating .I1 ofany of the cements known to be strongly adherent to metal and to rthe particular insulating plastic used, for example, a known composition kci? vinyl vchloridevinylacetate copolymer, with a thermosetting phenol-formaldehyde resin, and a glypatal resin in a suitable solvent and usually with suitable plasticizer or softener. VThis coating will conveniently be by dipping which has advantageaas indicated below.

After the tube I6 is thus coated, an outer insulating tube I8 is applied. The tube Igimayrcornprise any plasticY having toughnessto withstand the necessary crimping ,pressure without excessive cold'flovv. An extrusion cfvinyl chloride-'vinyl acetate copolymer plus a plasticizer such as tricresyl phosphate, -for example, may be slipped over tube I6 after being suiiiciently expanded either .by any .suitable mechanical stretching, or byimmersion in an organic solvent. The `solvent may include sufficient plasticizer to prevent excessive leaching creven to .increase the .proportion of plasticizerin the.,plastic; and .it is an advantage of this process that it Vpermits modication of the plastic to .giveyproper-.ties .-most suitable. lfor he .crimping operation, yeven through such Apropertiesunay .be-inconsistent with the .extrusion process by which the tubeis made. This leaching Witha `solvent aswell .asa ybaking hereafter mentioned are-the inventionrof Frank J. Sowaidescribed and claimed in afcopending application Serial No. 560,785, now abandoned, led Gctober.-2B,1\944.

If the tube i8 is mechanically expanded, it is subsequently shrunk :on inner `tube 1I 5 by Vnormal recovery with or without application of 'heat .to hasten such recovery. vIf the tube has been swelled 'a solvent, it shrinks N'onto the inner tube as soon a's"th'ev solvent 'evapora'tes.iL In ieither case the inner and/outer tubes are'tightly vbonded by the `coatingV II of cement which adheres to both. With the assembly as .-shown, the terminal is advantageously subjected to a heat treatment by which the cementcoating I"I -is'more securely bonded between the tube I'5ar1d the insulation I8. Thus the assembly may be baked or cured at a temperature of 250*J `F.-'300`F. Vfor iive to seven hours. I have also obtainedsatisfactory results .by baking at a somewhat higher temperature for a somewhat shorterperiod' of time. ,I believe that by so treating the assembly the 4plasticizer is substantially removed from the plastic sleeve, thus However, tube I E may be dispensed with and the insulation applied ldiv toughening it against flow or puncture during the crimping operation.

Of course, where inner tube I6 is not used, the coating II of cement is applied directly to ferrule I I, and the outer tube I8 is secured thereon in the manner described.

As shown, the sleeves I6 land I8 are longer than the ferrule II so that, after insulating sleeve I5, either with or without inner tube I6, has been slipped onto ferrule II and the end la of conductorV I4 is threaded into the ferrule a substantial portion of the .insulated part of the conductor lies within the ferrule, as shown in Figure 3. The filled ferrule is then placed between juxtaposed crimping dies which are closed with high pressur-e against opposite sides of sleeve I5. As the dies :engage vthe'insulation I8, crimps A, B and C are formed on one side, complementary crimps A1., B1 and C1 being formed on the opposite side. As shown in Figures 2 and 3, the plastic, the metal .sleeve I5, the ferrule II and the wire `I-A'Ia areall forged together under-the die .sothatall hold the impress of the die, but the insulating sleeve I8 is not punctured.

However, because of vthe tight bond between the insulation I 8 and tube i6., provided by cement I1., and because of the use of .a plastic having a tough leathery nature a-t ordinary temperatures thein-v sulating plastic It is not excessively extruded out from under the .crimping dies nor .is it sheared4 at the edges thereof, but rather .completely covers the surface of the crimp-so as to .leave no portion thereof exposed. .If anyshearingof ythe insulating plastic .should occur, it Wold befdue ,to .use-of too sharp corners -on the die ora plastic which 4,is too soft so that it is eas-ily extruded.; these conditions can be corrected. Even then .a l-mwof insulation ordinarily remains `and if the dieshould cut through to Athe metal, it would .only be ,at Jthe edges of the.die,..e. g. at points b and h1 of crimp B, where exposure .of the metal would be relatively:

harmless in .low voltage circuits. The bottom of the crimp would,- .of course, be completely. insu--` lated because theinsulating `plastic inthatarea would be tightly bonded to the metal ,tube or ferrule, as the case mightbeand thus-securely held against extrusion by the. pressure .of the Vcrimping die.

As noted above, metal tube .I 6 lpreferably formsV a part of sleeve .I5 whenferrule .II is seamed, fas at I I a. It may now be seen .that the combination of lthe .plastic .sleeve I5 and the tube I6, is Well able to resist and prevent spreading apartof the edges in ferrule II at Vseam II-a. Itis possible,l

howevento select an .insulating sleeve sufiicientl-y tough to serve this purpose without use-.of the metal tube .I B.

Thusl have providedan articlecf manufacture and a fabricating method .therefor which attainsy outer surface of said .ferrule .to the inner .surface of said tube.

2. An insulated electrical connectoras defined in claim 1 wherein .the tube is composedof a tough vinyl chloride-vinyl acetate copolymer plasticized 5 to an extent suiiicient to accommodate the deformation Without fracture.

3. An insulated electrical connector as defined in claim 1 wherein the ferrule is composed of soft pure electrical copper.

4. An insulated electrical connector as defined in claim 1 wherein the ferrule is composed of an inner metal tube adapted to t over the Wire and an outer metal tube tting over said inner tube.

ROBERT `C. SWENGEL.

6 References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Vinylite Resins for Surface Coatings, publication issued by Bakelite Corp., N. Y., copyright 1942, pages 20 and 21. 

